In general, a slot machine, which is one kind of gaming machine, includes, as an important component thereof, a symbol display unit for variably displaying and stopping a plurality of symbols for each column.
Such slot machines can be roughly divided, based on forms of the symbol display unit, into two types: those adopting a mechanical reel and those adopting a simulated reel as the symbol display unit. The mechanical reel type includes multiple reels having multiple kinds of symbol along the periphery, and the symbols can be variably displayed and stopped by mechanically rotating and stopping the reels. The combination of the stopped symbols may form a winning combination with which a player is awarded. And display effects are performed to amuse a player, as well as to inform the game state.
U.S. Pat. No. 5,752,881 discloses a gaming machine having outer and inner reels and a display window. A plurality of symbols are spaced peripherally about the outer reel. Each of the symbols is transparent with an opaque portion disposed inside and/or outside the transparent symbol. The inner reel is rotatable inside the outer reel. A plurality of different colored patterned portions are disposed in a peripheral series about the inner reel. One of the patterned portions stopped in the display window becomes observable through the transparent portion when the transparent symbol is stopped in the display window and is combined with the transparent symbol.
U.S. Pat. No. 7,380,791 discloses a gaming machine using controllable LEDs for reel strip illumination. A backlight for a reel assembly comprises a plurality of light emitting diodes (LEDs). An array of red, green, and blue diodes are positioned behind a translucent reel strip to backlight three adjacent symbols on a reel strip. The LEDs are individually controllable to vary the color output of the LED array for a full spectrum of colors, including white. Groups of LEDs can be illuminated to optimally illuminate any number of symbols of any size. The LEDs may be controlled to highlight special symbols such as by blinking or changing colors.